An SOI substrate generally includes a semiconductor film, for example of silicon or a silicon alloy, of uniform thickness, resting on a buried insulating layer, commonly referred to by the acronym “BOX” (Buried-OXide), which is itself situated above a supporting semiconductor substrate. In FDSOI technology, the semiconductor film is generally very thin (e.g., a few nanometres thick) and is fully depleted, which helps ensure desired electrostatic control.
Currently, to produce the insulation between these transistors, the production of the transistors is preceded by the formation of a shallow trench in the substrate, commonly referred to by the acronym “STI” (Shallow Trench Isolation), and more particularly in the semiconductor film. This creates separate domains in the semiconductor film that are electrically insulated from one another for the transistors, which are typically of a same conductivity type. However, since the space between the active zones (corresponding to the domains of the semiconductor films), in particular for insulating transistors of the same conductivity type, is becoming increasingly small due to technological refinements, the production of these trenches by photolithography is becoming more complicated.